This invention relates to the measurement of a parameter during manufacture of microminiature devices and, more particularly, during fabrication processes in which the temperature of a device substrate is to be measured in-situ.
For many device fabrication processes, it is important to be able to provide an accurate in-situ measurement of the temperature of a substrate (e.g., a wafer) on which a device is being fabricated in a processing chamber. By measuring substrate temperature, it is possible to accurately control temperature-dependent fabrication processes such as, for example, gas-phase etching and epitaxial growth. In that way, the task of making advanced devices with precisely predetermined dimensions and high-performance operating characteristics is facilitated.
Thermocouples of pyrometers are widely used for measuring temperature in a variety of applications. However, neither of these instrumentalities has been found to be suitable for directly measuring substrate temperature during fabrication of advanced devices. Thermocouples often give inaccurate readings due to poor thermal contact with the sample being monitored, while pyrometers typically require frequent and sometimes complicated calibration. Further, alternative temperature-measurement approaches, such as those based on transmission spectroscopy and laser interferometry, have often been found in practice to require unduly complex equipment and/or analysis.
Accordingly, efforts have continued by workers skilled in the art aimed at trying to devise a simple and accurate technique for in-situ temperature measurement of a device substrate. It was recognized that such efforts, if successful, could provide an important basis for lowering the cost of making high-performance microminiature devices.